Mechanochemically induced solid state transformations: The case of raloxifene hydrochloride.

Raloxifene hydrochloride is a benzothiophene derivative mainly used in the prevention and treatment of osteoporosis, but exhibits a low bioavailability hindered by its poor water solubility. In this study, a mechanochemical approach based on neat and liquid-assisted grinding was applied to produce new solid forms of raloxifene hydrochloride. The solids obtained were characterized by several solid-state techniques, such as powder X-ray diffraction, thermal analysis, infrared and Raman spectroscopy. These results showed that depending on the processing conditions solvated or amorphous forms can be produced. The thermal stability of the new forms was also investigated showing that the new forms convert back into the raw material form, as observed by Raman spectroscopy, which was successfully used to discriminate amorphous and crystalline forms, as well as, to monitor in situ the recrystallization process. Furthermore, the solubility of the new forms was evaluated, showing the clear advantage of the amorphous form, when compared with the currently marketed salt.

Novel polymorphs of the anti-Trypanosoma cruzi drug benznidazole.

Benznidazole (N-benzyl-2-(2-nitro-1H-imidazol-1-yl)acetamide), is a nitro-heterocyclic drug used in the treatment of Chagas disease. Despite the fact that this drug was released more than 30 years ago, little information about its solid state properties is available in the literature. In this study, it was verified that this drug exhibits three polymorphs, which were characterized in situ by X-ray powder diffraction, thermal analysis, hot stage microscopy and infrared spectroscopy. The thermodynamic relationships among these polymorphs were also discussed.

Role of hydrogen adsorption on the carbon terminated ß-SiC(100)-c(2 × 2) surface structure: a theoretical approach.

The role of hydrogen adsorption on different clean surface models for the carbon terminated ß-SiC(100)-c(2 × 2) surface structure is investigated through the use of ab initio calculations. The structural and electronic effect of hydrogen atoms bonded to carbon and/or silicon dimers is specifically considered and compared with the results for a clean surface model. The presence of adsorbed hydrogen atoms affects the atomic equilibrium positions, as well as electronic properties, of the atoms of the clean structure. These last properties are altered in different directions if the adsorption occurs in one or the other of the two investigated models. The changes in both structural and electronic properties were evaluated and compared with those of the clean surface. From our obtained results, a possible metallization, as a result of hydrogen adsorption, is theoretically postulated to occur in a similar way to what occurs with the silicon terminated ß-SiC(100)(3 × 2) surface.